export class path {
    static join(...parts: string[]) {
        if (arguments.length === 0)
            return '.';
        var joined;
        for (var i = 0; i < arguments.length; ++i) {
            var arg = arguments[i];
            if (arg.length > 0) {
                if (joined === undefined)
                    joined = arg;
                else
                    joined += '/' + arg;
            }
        }
        if (joined === undefined)
            return '.';
        return this.posixNormalize(joined);
    }

    static dirname(path: string) {
        if (path.length === 0) return '.';
        var code = path.charCodeAt(0);
        var hasRoot = code === 47 /*/*/;
        var end = -1;
        var matchedSlash = true;
        for (var i = path.length - 1; i >= 1; --i) {
            code = path.charCodeAt(i);
            if (code === 47 /*/*/) {
                if (!matchedSlash) {
                    end = i;
                    break;
                }
            } else {
                // We saw the first non-path separator
                matchedSlash = false;
            }
        }

        if (end === -1) return hasRoot ? '/' : '.';
        if (hasRoot && end === 1) return '//';
        return path.slice(0, end);
    }

    static basename(path: string, ext?: string) {
        if (ext !== undefined && typeof ext !== 'string') throw new TypeError('"ext" argument must be a string');

        var start = 0;
        var end = -1;
        var matchedSlash = true;
        var i;

        if (ext !== undefined && ext.length > 0 && ext.length <= path.length) {
            if (ext.length === path.length && ext === path) return '';
            var extIdx = ext.length - 1;
            var firstNonSlashEnd = -1;
            for (i = path.length - 1; i >= 0; --i) {
                var code = path.charCodeAt(i);
                if (code === 47 /*/*/) {
                    // If we reached a path separator that was not part of a set of path
                    // separators at the end of the string, stop now
                    if (!matchedSlash) {
                        start = i + 1;
                        break;
                    }
                } else {
                    if (firstNonSlashEnd === -1) {
                        // We saw the first non-path separator, remember this index in case
                        // we need it if the extension ends up not matching
                        matchedSlash = false;
                        firstNonSlashEnd = i + 1;
                    }
                    if (extIdx >= 0) {
                        // Try to match the explicit extension
                        if (code === ext.charCodeAt(extIdx)) {
                            if (--extIdx === -1) {
                                // We matched the extension, so mark this as the end of our path
                                // component
                                end = i;
                            }
                        } else {
                            // Extension does not match, so our result is the entire path
                            // component
                            extIdx = -1;
                            end = firstNonSlashEnd;
                        }
                    }
                }
            }

            if (start === end) end = firstNonSlashEnd; else if (end === -1) end = path.length;
            return path.slice(start, end);
        } else {
            for (i = path.length - 1; i >= 0; --i) {
                if (path.charCodeAt(i) === 47 /*/*/) {
                    // If we reached a path separator that was not part of a set of path
                    // separators at the end of the string, stop now
                    if (!matchedSlash) {
                        start = i + 1;
                        break;
                    }
                } else if (end === -1) {
                    // We saw the first non-path separator, mark this as the end of our
                    // path component
                    matchedSlash = false;
                    end = i + 1;
                }
            }

            if (end === -1) return '';
            return path.slice(start, end);
        }
    }

    static extname(path: string) {
        var startDot = -1;
        var startPart = 0;
        var end = -1;
        var matchedSlash = true;
        // Track the state of characters (if any) we see before our first dot and
        // after any path separator we find
        var preDotState = 0;
        for (var i = path.length - 1; i >= 0; --i) {
            var code = path.charCodeAt(i);
            if (code === 47 /*/*/) {
                // If we reached a path separator that was not part of a set of path
                // separators at the end of the string, stop now
                if (!matchedSlash) {
                    startPart = i + 1;
                    break;
                }
                continue;
            }
            if (end === -1) {
                // We saw the first non-path separator, mark this as the end of our
                // extension
                matchedSlash = false;
                end = i + 1;
            }
            if (code === 46 /*.*/) {
                // If this is our first dot, mark it as the start of our extension
                if (startDot === -1)
                    startDot = i;
                else if (preDotState !== 1)
                    preDotState = 1;
            } else if (startDot !== -1) {
                // We saw a non-dot and non-path separator before our dot, so we should
                // have a good chance at having a non-empty extension
                preDotState = -1;
            }
        }

        if (startDot === -1 || end === -1 ||
            // We saw a non-dot character immediately before the dot
            preDotState === 0 ||
            // The (right-most) trimmed path component is exactly '..'
            preDotState === 1 && startDot === end - 1 && startDot === startPart + 1) {
            return '';
        }
        return path.slice(startDot, end);
    }



    static parse(path: string) {

        var ret = { root: '', dir: '', base: '', ext: '', name: '' };
        if (path.length === 0) return ret;
        var code = path.charCodeAt(0);
        var isAbsolute = code === 47 /*/*/;
        var start;
        if (isAbsolute) {
            ret.root = '/';
            start = 1;
        } else {
            start = 0;
        }
        var startDot = -1;
        var startPart = 0;
        var end = -1;
        var matchedSlash = true;
        var i = path.length - 1;

        // Track the state of characters (if any) we see before our first dot and
        // after any path separator we find
        var preDotState = 0;

        // Get non-dir info
        for (; i >= start; --i) {
            code = path.charCodeAt(i);
            if (code === 47 /*/*/) {
                // If we reached a path separator that was not part of a set of path
                // separators at the end of the string, stop now
                if (!matchedSlash) {
                    startPart = i + 1;
                    break;
                }
                continue;
            }
            if (end === -1) {
                // We saw the first non-path separator, mark this as the end of our
                // extension
                matchedSlash = false;
                end = i + 1;
            }
            if (code === 46 /*.*/) {
                // If this is our first dot, mark it as the start of our extension
                if (startDot === -1) startDot = i; else if (preDotState !== 1) preDotState = 1;
            } else if (startDot !== -1) {
                // We saw a non-dot and non-path separator before our dot, so we should
                // have a good chance at having a non-empty extension
                preDotState = -1;
            }
        }

        if (startDot === -1 || end === -1 ||
            // We saw a non-dot character immediately before the dot
            preDotState === 0 ||
            // The (right-most) trimmed path component is exactly '..'
            preDotState === 1 && startDot === end - 1 && startDot === startPart + 1) {
            if (end !== -1) {
                if (startPart === 0 && isAbsolute) ret.base = ret.name = path.slice(1, end); else ret.base = ret.name = path.slice(startPart, end);
            }
        } else {
            if (startPart === 0 && isAbsolute) {
                ret.name = path.slice(1, startDot);
                ret.base = path.slice(1, end);
            } else {
                ret.name = path.slice(startPart, startDot);
                ret.base = path.slice(startPart, end);
            }
            ret.ext = path.slice(startDot, end);
        }

        if (startPart > 0) ret.dir = path.slice(0, startPart - 1); else if (isAbsolute) ret.dir = '/';

        return ret;
    }




    static posixNormalize(path: string) {

        if (path.length === 0) return '.';

        var isAbsolute = path.charCodeAt(0) === 47 /*/*/;
        var trailingSeparator = path.charCodeAt(path.length - 1) === 47 /*/*/;

        // Normalize the path
        path = this.normalizeStringPosix(path, !isAbsolute);

        if (path.length === 0 && !isAbsolute) path = '.';
        if (path.length > 0 && trailingSeparator) path += '/';

        if (isAbsolute) return '/' + path;
        return path;
    }

    static normalizeStringPosix(path: string, allowAboveRoot: boolean) {
        var res = '';
        var lastSegmentLength = 0;
        var lastSlash = -1;
        var dots = 0;
        var code;
        for (var i = 0; i <= path.length; ++i) {
            if (i < path.length)
                code = path.charCodeAt(i);
            else if (code === 47 /*/*/)
                break;
            else
                code = 47 /*/*/;
            if (code === 47 /*/*/) {
                if (lastSlash === i - 1 || dots === 1) {
                    // NOOP
                } else if (lastSlash !== i - 1 && dots === 2) {
                    if (res.length < 2 || lastSegmentLength !== 2 || res.charCodeAt(res.length - 1) !== 46 /*.*/ || res.charCodeAt(res.length - 2) !== 46 /*.*/) {
                        if (res.length > 2) {
                            var lastSlashIndex = res.lastIndexOf('/');
                            if (lastSlashIndex !== res.length - 1) {
                                if (lastSlashIndex === -1) {
                                    res = '';
                                    lastSegmentLength = 0;
                                } else {
                                    res = res.slice(0, lastSlashIndex);
                                    lastSegmentLength = res.length - 1 - res.lastIndexOf('/');
                                }
                                lastSlash = i;
                                dots = 0;
                                continue;
                            }
                        } else if (res.length === 2 || res.length === 1) {
                            res = '';
                            lastSegmentLength = 0;
                            lastSlash = i;
                            dots = 0;
                            continue;
                        }
                    }
                    if (allowAboveRoot) {
                        if (res.length > 0)
                            res += '/..';
                        else
                            res = '..';
                        lastSegmentLength = 2;
                    }
                } else {
                    if (res.length > 0)
                        res += '/' + path.slice(lastSlash + 1, i);
                    else
                        res = path.slice(lastSlash + 1, i);
                    lastSegmentLength = i - lastSlash - 1;
                }
                lastSlash = i;
                dots = 0;
            } else if (code === 46 /*.*/ && dots !== -1) {
                ++dots;
            } else {
                dots = -1;
            }
        }
        return res;
    }

    static posixResolve(...args: string[]) {
        var resolvedPath = '';
        var resolvedAbsolute = false;
        var cwd;

        for (var i = args.length - 1; i >= -1 && !resolvedAbsolute; i--) {
            var path;
            if (i >= 0)
                path = args[i];
            else {
                if (cwd === undefined)
                    cwd = process.cwd();
                path = cwd;
            }


            // Skip empty entries
            if (path.length === 0) {
                continue;
            }

            resolvedPath = path + '/' + resolvedPath;
            resolvedAbsolute = path.charCodeAt(0) === 47 /*/*/;
        }

        // At this point the path should be resolved to a full absolute path, but
        // handle relative paths to be safe (might happen when process.cwd() fails)

        // Normalize the path
        resolvedPath = this.normalizeStringPosix(resolvedPath, !resolvedAbsolute);

        if (resolvedAbsolute) {
            if (resolvedPath.length > 0)
                return '/' + resolvedPath;
            else
                return '/';
        } else if (resolvedPath.length > 0) {
            return resolvedPath;
        } else {
            return '.';
        }
    }

    static relative(from: string, to: string) {

        if (from === to) return '';

        from = this.posixResolve(from);
        to = this.posixResolve(to);

        if (from === to) return '';

        // Trim any leading backslashes
        var fromStart = 1;
        for (; fromStart < from.length; ++fromStart) {
            if (from.charCodeAt(fromStart) !== 47 /*/*/)
                break;
        }
        var fromEnd = from.length;
        var fromLen = fromEnd - fromStart;

        // Trim any leading backslashes
        var toStart = 1;
        for (; toStart < to.length; ++toStart) {
            if (to.charCodeAt(toStart) !== 47 /*/*/)
                break;
        }
        var toEnd = to.length;
        var toLen = toEnd - toStart;

        // Compare paths to find the longest common path from root
        var length = fromLen < toLen ? fromLen : toLen;
        var lastCommonSep = -1;
        var i = 0;
        for (; i <= length; ++i) {
            if (i === length) {
                if (toLen > length) {
                    if (to.charCodeAt(toStart + i) === 47 /*/*/) {
                        // We get here if `from` is the exact base path for `to`.
                        // For example: from='/foo/bar'; to='/foo/bar/baz'
                        return to.slice(toStart + i + 1);
                    } else if (i === 0) {
                        // We get here if `from` is the root
                        // For example: from='/'; to='/foo'
                        return to.slice(toStart + i);
                    }
                } else if (fromLen > length) {
                    if (from.charCodeAt(fromStart + i) === 47 /*/*/) {
                        // We get here if `to` is the exact base path for `from`.
                        // For example: from='/foo/bar/baz'; to='/foo/bar'
                        lastCommonSep = i;
                    } else if (i === 0) {
                        // We get here if `to` is the root.
                        // For example: from='/foo'; to='/'
                        lastCommonSep = 0;
                    }
                }
                break;
            }
            var fromCode = from.charCodeAt(fromStart + i);
            var toCode = to.charCodeAt(toStart + i);
            if (fromCode !== toCode)
                break;
            else if (fromCode === 47 /*/*/)
                lastCommonSep = i;
        }

        var out = '';
        // Generate the relative path based on the path difference between `to`
        // and `from`
        for (i = fromStart + lastCommonSep + 1; i <= fromEnd; ++i) {
            if (i === fromEnd || from.charCodeAt(i) === 47 /*/*/) {
                if (out.length === 0)
                    out += '..';
                else
                    out += '/..';
            }
        }

        // Lastly, append the rest of the destination (`to`) path that comes after
        // the common path parts
        if (out.length > 0)
            return out + to.slice(toStart + lastCommonSep);
        else {
            toStart += lastCommonSep;
            if (to.charCodeAt(toStart) === 47 /*/*/)
                ++toStart;
            return to.slice(toStart);
        }
    }
}